1. Field of the Invention
The present invention is generally directed toward an acid-functionalized nanoparticle and uses thereof as catalysts in hydrolysis reactions, particularly in ring opening of epoxidized plant oils such as epoxidized soybean oils and the conversion of cellulose into fructose and 2,5-dimethyl-furan.
2. Description of the Prior Art
Epoxidized soybean oil (ESO), a well-known and commercially available functionalized plant oil as a plasticizer in the plastics industry, is amenable to hydrolysis using conventional chemical methodology of ring-opening reaction of oxirane moieties. Hydroxyl soybean oil called soy polyol is produced from ESO via α-methoxy-hydroxylation and is widely used for polyurethane applications. Plant oil-based polyol show better environmental benefits than petroleum-based polyols because of the former's significantly lowered greenhouse gas emissions.
The global market for polyols is forecasted to reach 4 billion pounds by the year 2015. Recently, Recticel (Evere, Belgium), the largest polyurethane manufacturer in Europe, has started to produce foams using BiOH® (Cargill Inc., Minneapolis, Minn.). Although soy polyols were derived from biobased feedstocks, synthetic methods for most soy polyol production do not emphasize green chemistry, which has been spotlighted recently because of stricter government regulations regarding sustainability.
The term green chemistry was comprehensively defined by Anastas and Warner as “the utilization of a set of principles that reduces or eliminates the use or generation of hazardous substance in the design, manufacture and application of chemical products” with 12 principles: 1) prevention, 2) atom economy, 3) less hazardous chemical syntheses, 4) safer chemicals, 5) safer solvents and auxiliaries, 6) energy efficiency, 7) use of renewable feedstocks, 8) derivatives reduction, 9) catalysis, 10) design for degradation, 11) real-time analysis for pollution prevention, and 12) inherently safer chemistry for accident prevention. In terms of green chemistry, a common problem in the synthesis of α-methoxy-hydroxylation from epoxidized oleo-chemicals is the need for strong Brønsted acids to activate the epoxide ring toward the attack of weakly nucleophilic alcohols. This has been accomplished through the action of strong homogeneous acids such as HCl, HBr, or p-toluenesulfonic acid. Even formic acid (a milder acid) has been shown to accomplish one-pot synthesis of soy polyols, although this reaction presented low reaction selectivity (non-homogeneous distribution and oligomerization) and low conversion yield (residual epoxides). All cases require the removal of acid, solvent purification steps, and high temperature, which generates carbon emissions and undesirable byproducts such as ketones. Green chemistry researchers have become interested in solid acid catalysts (e.g., zeolites, heteropolyacids, and ion-exchange resins), which, if they replaced the numerous tons of non-recyclable homogeneous acid catalysts consumed annually in current industrial processes, would minimize environmental defects including waste generation.
Heterogeneous catalysts have shown potential as replacements for traditional homogeneous acid-catalyzed processes, including biodiesel production. Rios et al. presented ring opening of epoxidized methyl oleate using commercial heterogeneous acid resin catalysts such as SAC 13 and Amberlite 15; however, the commercial heterogeneous solid catalysts recorded lower product yield and higher energy consumption than homogeneous sulfuric acid in the ring opening of epoxidized methyl oleate (EMO). See, L. A. Rios, et al., Appl. Catal., A, 2005, 284, 155-161. Increased activity and stability has been shown using sulfonic acid-functionalized mesostructured silica, this technique carries the inconvenience of the resin swelling.